In the original Fallout games everything was viewed from an isometric perspective, giving you a fairly generous view of your character and the surrounding environment. In standard play you'd be free to move around as you wish, but whenever a fight broke out the game would shift to a turn-based system. Depending on your character's Agility rating, you'd have a number of action points (AP) which could be spent on moving, firing weapons and accessing your inventory. Now, this setup may sound totally archaic to some modern gamers, but the fact is that it resulted in a high degree of tactical consideration....
As you probably know by now, Fallout 3 is primarily a first-person game; a third-person perspective is available, but we can't see many people using it for any length of time. While you can choose to play the whole game as a real-time shooter, you'll find it much easier to use the VATS system, which allows you to pause time and queue up a limited number of AP on targeted shots. There's certainly a degree of similarity to the old games here, with an emphasis on blinding or crippling your opponent - but you'll rarely have enough points to end a battle using VATS alone. We've found that in practice we tend to soften the enemy up with a few manually-aimed shots, before switching to VATS to make a few decisive hits. It's not exactly old-school Fallout, but it's not Doom either. It is, however, very satisfying. We were a bit worried that VATS might get old quite quickly, but we now believe the balance of its use is just about right.
